In court documents, prosecutors working for the special counsel, Robert S. Mueller III, said that Mr. Manafort tried to contact witnesses by phone and through an encrypted messaging program...

The communications were an "effort to influence their testimony and to otherwise hide evidence", FBI Special Agent Brock Domin wrote in a declaration filed to court alongside Mr Mueller's motion. The texts started in late February, just after Mueller unsealed a new set of charges against Manafort in Washington, D.C., the prosecutors said.

The FBI has documents and statements from the two people, as well as telephone records and documents recovered through a search of Mr. Manafort's iCloud account showing that the President's former campaign manager attempted communication while he was out on bail, according to Mr. Domin.

"Person D2 explained that he and Person D1 had been responsible for interfacing with the Hapsburg group, and acted as "intermediaries" between Manafort and Ukraine government officials and the Hapsburg group", prosecutors wrote.

They have asked federal judges to revise or revoke his terms of release meaning the President's former campaign manager could face imprisonment until his trial. Evidence included documents and testimony from the two PR people, as well as phone records and "documents recovered pursuant to a court-authorized search of Manafort's iCloud account", according to a declaration from an Federal Bureau of Investigation agent involved in the case.

In one call, the agent wrote, Manafort said he wanted to give the witness a "heads-up about Hapsburg".

In previous filings, Person A has been used to designate Konstantin Kilimnik, a Manafort associate who prosecutors believe has ties to Russian intelligence - something Kilimnik has denied.

The FBI reportedly opened a criminal investigation of Manafort in 2014. The individual immediately ended the call "because he was concerned about the outreach", according to the affidavit. He has pleaded not guilty.

The day after the Superseding Indictment was made public, Manafort also sent Person D1 a text message on an encrypted application, stating "This is paul". One of the messages was a link to a newspaper article, while the other was an invitation to talk and a warning that he "made clear" to the investigators that the activities of the group were limited to Europe. I think, however, they were doing a number on Trump himself. Both witnesses said that wasn't true.